Method for cracking and separating pellets formed on a wafer

Abstract

A method for protecting electronic circuitry formed on the obverse side of a wafer from flying debris produced either by the mechanical or laser scribing or scoring of the wafer and during separation. The device is provided with a layer of abrasion resistant material on the circuit side of the wafer and the scribing or scoring is done on the obverse side of the wafer. The cracking operation is performed by applying pressure to the wafer in such a manner as to have the reverse side in tension and the obverse or circuit side in compression in order to prevent any debris which may have been cast up during the scribing or scoring operation from contaminating or damaging the circuit side of the wafer while any debris cast up during the breaking operation is thrown away from the obverse or circuit side.

What is claimed is: 
     
       1. A method of separating individual semiconductor circuit elements from a wafer on the obverse side of which the individual circuit elements were formed, the wafer being scored along lines arranged in rows and columns to define the boundary limits of the individual circuit elements comprising the steps of: applying a soft, resilient, adherent protective layer to the circuit elements on the obverse side of the wafer, the layer characterized by having the ability to return to its original form after being deformed;   scoring the wafer on the reverse side thereof to define the boundary limits of the individual circuit elements; and   applying a breaking force to the obverse side of the wafer to separate the individual circuit elements, one from the other, along the scored lines.   
     
     
       2. The method of claim 1, wherein: the wafer is selected from the group consisting of sapphire, spinel or monocrystalline aluminum oxide; and   the circuit elements are formed in silicon islands on the obverse side of the wafer.   
     
     
       3. The method of claim 2, wherein: the breaking force is applied by means of a round, elongated mandrel; and   the mandrel is forced under pressure, across the obverse side of the wafer.   
     
     
       4. The method of claim 3, wherein: the mandrel is first forced across the wafer in a direction parallel to the scored row lines; and   the mandrel is next forced across the wafer in a direction parallel to the scored column lines.   
     
     
       5. The method of claim 2, comprising the further steps of: providing a mandrel with a convex hemispherical shape having a surface area at least equal to the surface area of the wafer;   providing a complementary concave surface for mating with the convex hemisphere;   positioning the wafer on the convex hemisphere with the scored reverse side facing the concave surface; and   forcing the convex hemisphere and the concave surface into mating relationship whereby the wafer therebetween is broken into individual circuit elements along the scored lines.